Polymerisation inhibitors

Abstract

The present invention relates to a mixture containing at least one 1,2,3,4-tetrahydroquinoxaline and at least one polymerisable carbonyl compound.

Description

[0001] Polymerization inhibitors

[0002] The present invention relates to a mixture containing at least one substituted 1,2,3,4-tetrahydroquinoxaline and at least one polymerizable carbonyl compound.

[0003] Chemical compounds that contain one or more ethylenically unsaturated groups have a pronounced tendency toward radical polymerization. Such compounds are therefore also referred to as polymerizable compounds. Due to their tendency toward radical polymerization, these compounds are used as monomers for the production of polymers. However, the pronounced tendency of these compounds toward radical polymerization is disadvantageous in that it can lead to undesirable, spontaneous radical polymerization during storage and transport, as well as during chemical and / or physical processing, such as distillation or rectification, particularly under the influence of energy, such as heat and / or light.Such uncontrolled polymerizations can lead to the gradual formation of polymer deposits, for example, on heated surfaces, necessitating their removal and thus often resulting in a reduction in operating times. Uncontrolled polymerizations can even be explosive.

[0004] It is therefore common practice to add compounds that inhibit or at least slow down unwanted, spontaneous radical polymerization to ethylenically unsaturated compounds that have a tendency toward radical polymerization, or to mixtures containing such compounds, both during storage and transport and during chemical and / or physical processing. Such substances are referred to as polymerization inhibitors.

[0005] Polymerization inhibitors can be used as individual chemical compounds or as mixtures of compounds. Depending on the application, specific requirements apply to the polymerization inhibitor. For a polymerization inhibitor to be suitable as a transport and / or storage stabilizer for ethylenically unsaturated compounds, it is important that the efficiency of the polymerization inhibitor, i.e., the extent of polymerization inhibition, can be regulated.Under the storage and / or transport conditions of the ethylenically unsaturated compounds, the polymerization inhibitor should sufficiently prevent or slow down the undesired, spontaneous radical polymerization, whereas the desired radical polymerization of the ethylenically unsaturated compounds should be possible under appropriate polymerization conditions without the need to first separate the polymerization inhibitor used during storage and / or transport. If the stabilizer used during storage and / or transport is not separated during the desired polymerization, it is important that it does not adversely affect the desired polymerization, for example, by acting unintentionally as a regulator.

[0006] Measured by global production volume, acrylic acid is certainly one of the most important ethylenically unsaturated compounds. Acrylic acid is typically stabilized against unwanted, spontaneous radical polymerization during storage and / or transport with 0.018 to 0.022 wt.% hydroquinone monomethyl ether (MEHQ), based on the amount of acrylic acid. For adequate stabilization of acrylic acid against unwanted, spontaneous radical polymerization using MEHQ, it is necessary that oxygen is dissolved in the acrylic acid in sufficient quantities. Sufficient amounts of oxygen are usually dissolved in the acrylic acid when acrylic acid is stored and / or transported under an atmosphere containing 5 to 21 vol.% oxygen.During the desired polymerization of acrylic acid, the oxygen content dissolved in the acrylic acid is reduced, thereby reducing the efficiency of MEHQ to inhibit polymerization to such an extent that acrylic acid can be polymerized in the presence of MEHQ.

[0007] In addition to its use as a polymerization inhibitor during storage and / or transport of acrylic acid, MEHQ is also used as a polymerization inhibitor during storage and / or transport of methacrylic acid, acrylic acid esters and / or methacrylic acid esters or mixtures containing one or more of the aforementioned compounds.

[0008] Due to its wide use, MEHQ is one of the most important storage and / or transport stabilizers for polymerizable compounds, especially for acrylic acid, methacrylic acid, acrylic acid esters and methacrylic acid esters.

[0009] Polymerizable compounds are stored in suitable, permanently installed containers, such as storage tanks or storage containers (see, for example, Acrylic Acid, A Summary of Safety and Handling, 4th Edition 2013, 7 Bulk Storage Facilities and Accessories). It is preferred that the polymerizable compounds remain in the respective containers for at least one minute during storage, more preferably at least 10 minutes, and most preferably at least 60 minutes. Although the storage period is theoretically unlimited under appropriate conditions, the storage period is generally reduced to a minimum for economic reasons. It is preferred that the polymerizable compounds remain in the respective containers for a maximum of 180 days, more preferably for a maximum of 90 days, and most preferably for a maximum of 30 days.Particularly preferred ranges result from any combination of the previously mentioned lower and upper limits.

[0010] Polymerizable compounds are usually transported in suitable, transportable containers such as tanks or containers by ship, railcar, and / or truck (see, for example, Acrylic Acid, A Summary of Safety and Handling, 4th Edition 2013, 9 Safe Transport of Acrylic Acid). Transportable containers can also be permanently installed on the respective means of transport, such as ship tanks or rail tank cars. It is also possible for the containers to be stored at a specific location for a certain period of time before being transported to another location. Polymerizable compounds can also be transported in pipelines or hoses, for example, after purification of the polymerizable compounds to the storage tank, during loading from the storage tank into a transportable container, and / or during loading from one transportable container to another.It is preferred that the polymerizable compounds remain in the respective containers for at least 10 seconds, preferably at least one minute, more preferably at least 10 minutes, and most preferably at least 60 minutes, during transport. Although the duration is theoretically unlimited under appropriate conditions, the duration is generally reduced to a minimum for economic and safety reasons. It is preferred that the polymerizable compounds remain in the respective containers for a maximum of 180 days, more preferably for a maximum of 90 days, and most preferably for a maximum of 30 days, during transport. Particularly preferred ranges result from any combination of the aforementioned lower and upper limits.

[0011] The object of the present invention was to provide mixtures containing at least one polymerizable carbonyl compound, in particular acrylic acid, methacrylic acid, acrylic acid esters, and / or methacrylic acid esters, and at least one polymerization inhibitor. The polymerization inhibitors are intended to ensure sufficient stabilization of the polymerizable compounds against unwanted radical polymerization. However, in the case of desired radical polymerization, there should be no need to separate the polymerization inhibitors from the mixture prior to polymerization. The polymerization inhibitors should therefore not act as polymerization regulators and / or polymerization inhibitors in the desired radical polymerization.

[0012] The object is achieved by mixtures containing at least one compound of the general formula (I) where

[0013] R 1 , R2 , R 3 and R 4 independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide,

[0014] R 5 H, Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl,

[0015] R 6 , R 7 , R 8 and R 9 independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide and

[0016] R 10 H, Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl, or a compound of the general formula (II) where

[0017] R 11 , R 12 , R 13 and R 14 independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide,

[0018] R 15H, Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl,

[0019] R 16 and R 17 independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide and

[0020] R 18 H, C1- to C20-alkyl, C1- to C20-acyl, or aryl, and at least one polymerizable carbonyl compound, wherein the total amount of the polymerizable carbonyl compound in the mixture is at least 30 wt.%, based on the total weight of the mixture. The polymerizable carbonyl compounds are among the polymerizable compounds. The polymerizable carbonyl compounds are preferably ethylenically unsaturated carbonyl compounds.

[0021] The alkyl groups can be straight, branched and / or cyclic, whereby branched and cyclic alkyl compounds would only be possible from Ce-alkyl onwards.

[0022] Preferred is R 1 , R 2 , R 3 and R 4 independently of one another H, Ci- to Cw-alkyl, Ci- to Cw-alkoxy, hydroxy or halide, R 5 H or Ci- to Cw-alkyl, R 6 , R 7 , R 8 and R 9 independently of one another H, Ci- to Cw-alkyl, Ci- to Cw-alkoxy, hydroxy or halide and R 10 H or Ci- to Cw-alkyl, and R 11 , R 12 , R 13 and R 14 independently of one another H, Ci- to Cw-alkyl, Ci- to Cw-alkoxy, hydroxy or halide, R 15 H or Ci- to Cw-alkyl, R 16 and R 17 independently of one another H, Ci- to Cw-alkyl, Ci- to Cw-alkoxy, hydroxy or halide and R 18 H or Ci- to Cw-alkyl.

[0023] Further preferred is R 1 , R 2 , R 3 and R 4 independently of one another H, Ci- to Ce-alkyl or Ci- to Ce-alkoxy, R 5 H or Ci- to Ce-alkyl, R 6 , R7 , R 8 and R 9 independently of one another H, Ci- to Ce-alkyl or Ci- to Ce-alkoxy and R 10 H or Ci- to Ce-alkyl, and R 11 , R 12 , R 13 and R 14 independently of one another H, Ci- to Ce-alkyl or Ci- to Ce-alkoxy, R 15 H or Ci- to Ce-alkyl, R 16 and R 17 independently of one another H, Ci- to Ce-alkyl or Ci- to Ce-alkoxy and R 18 H or Ci- to Ce-alkyl. R is particularly preferably 1 , R 2 , R 3 and R 4 independently of one another H, Ci- to C lkyl or Ci- to C ikoxy, R 5 H or Ci- to Cs-alkyl, R 6 , R 7 , R 8 and R 9 independently of one another H, Ci- to C lkyl or Ci- to C ikoxy and R 10 H or Ci- to Cs-alkyl, and R 11 , R 12 , R 13 and R 14 independently of one another H, Ci- to C lkyl or Ci- to C ikoxy, R 15 H or Ci- to Cs-alkyl, R16 and R 17 independently of one another H, Ci- to C lkyl or Ci- to C ikoxy and R 18 H or Ci- to Cs-alkyl.

[0024] Especially preferred is R 1 , R 2 , R 3 and R 4 independently of one another H, Ci- to C2-alkyl or Ci- to C2-alkoxy, R 5 H or Ci- to C2-alkyl, R 6 , R 7 , R 8 and R 9 independently of one another H, Ci- to C2-alkyl or Ci- to C2-alkoxy and R 10 H or Ci- to C2-alkyl, and R 11 , R 12 , R 13 and R 14 independently of one another H, Ci- to C2-alkyl or Ci- to C2-alkoxy, R 15 H or Ci- to C2-alkyl, R 16 and R 17 independently of one another H, Ci- to C2-alkyl or Ci- to C2-alkoxy and R 18 H or Ci- to C2-alkyl.

[0025] Geeignete Verbindungen der allgemeinen Formel (I) sind beispielsweise 1 ,2,3,4-Tetrahydroquinoxalin, 1-Methyl- 1 ,2,3,4-Tetrahydroquinoxalin, 2-Methyl-1 ,2,3,4-Tetrahydroquinoxalin, 5-Methyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Me- thyl-1 ,2,3,4-Tetrahydroquinoxalin, 1-Ethyl-1,2,3,4-Tetrahydroquinoxalin, 2-Ethyl-1 ,2,3,4-Tetrahydroquinoxalin, 5- Ethyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Ethyl-1,2,3,4-Tetrahydroquinoxalin, 1-Propyl-1,2,3,4-Tetrahydroquinoxalin, 2- Propyl-1 ,2,3,4-Tetrahydroquinoxalin, 5-Propyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Propyl-1 ,2,3,4-Tetrahydroquinoxalin, 1-Butyl-1,2,3,4-Tetrahydroquinoxalin, 2-Butyl-1,2,3,4-Tetrahydroquinoxalin, 5-Butyl-1,2,3,4-Tetrahydroquinoxalin, 6- Butyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0026] 1-Phenyl-1 ,2,3,4-Tetrahydroquinoxalin, 2-Phenyl-1 ,2,3,4-Tetrahydroquinoxalin, 5-Phenyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Phenyl-1,2,3,4-Tetrahydroquinoxalin, 1-Benzyl-1 ,2,3,4-Tetrahydroquinoxalin, 2-Benzyl-1 ,2,3,4-Tetrahydroqui- noxalin, 5-Benzyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Benzyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0027] 2,2-Dimethyl-1,2,3,4-Tetrahydroquinoxalin, 2,2-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,2-Dipropyl-1,2,3,4-Tetrahydro- quinoxalin, 2,2-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,3-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,3-diethyl-1 ,2,3,4- Tetrahydroquinoxalin, 2,3-Dipropyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,3-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,5-Dime- thyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,5-diethyl-1,2,3,4-Tetrahydroquinoxalin, 2,5-Dipropyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,5-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,6-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,6-diethyl-1 ,2,3,4-Tetrahyd- roquinoxalin, 2,6-Dipropyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,6-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin, 2, 7-Dimethyl- 1,2,3,4-Tetrahydroquinoxalin, 2,7-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,7-Dipropyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,7-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,8-Dimethyl-1,2,3,4-Tetrahydroquinoxalin, 2,8-diethyl-1,2,3,4-Tetrahydro- quinoxalin, 2,8-Dipropyl-1 ,2,3,4-Tetrahydroquinoxalin, 2,8-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0028] 1,2-Dimethyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,2-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2-Dipropyl-1,2,3,4-Tetrahydro- quinoxalin, 1,2-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,3-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3-diethyl-1 ,2,3,4- Tetrahydroq uinoxal in , 1 , 3-D i propyl- 1 , 2, 3, 4-Tetrahy droq uinoxal i n, 1 , 3-D i buty I- 1 , 2, 3, 4-Tetrahydroq uinoxal in , 1 ,4-Dime- thyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,4-diethyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,4-Dipropyl-1 ,2,3,4-Tetrahydroquinoxa- lin, 1 ,4-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,5-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,5-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 , 5-D i propyl- 1 ,2,3,4-Tetrahydroquinoxalin, 1 , 5-Di butyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,6-Dimethyl-

[0029] 1.2.3.4-Tetrahydroquinoxalin, 1 ,6-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,6-Dipropyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0030] 1.6-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,7-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,7-diethyl-1,2,3,4-Tetrahydro- quinoxalin, 1 , 7-Dipropy I- 1 ,2,3,4-Tetrahydroquinoxalin, 1 , 7-Dibutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,8-Dimethy 1-1 ,2,3,4- Tetrahydroquinoxalin, 1 ,8-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,8-Dipropyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,8-Di- butyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0031] 1,2,3-Trimethyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,2,3-Triethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,3-Tripropyl-1 ,2,3,4- Tetrahydroquinoxalin, 1 ,2,3-Tributyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,3,4-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0032] 1.2.3.4-Tetraethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,3,4-Tetrapropyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,2,3,4-Tetrabutyl-

[0033] 1.2.3.4-Tetrahydroquinoxalin. 1 ,2,3,4,5-Pentamethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 , 2,3,4, 5-Pentaethyl-1, 2,3, 4-Tet- rahydroquinoxalin, 1 ,2,3,4,5-Pentapropyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,3,4,5-Pentabutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,3,4,5,6-Hexamethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,2,3,4,5,6-Hexaethyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0034] 1.2.3.4.5.6-Hexapropyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,3,4,5,6-Hexabutyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0035] 1.2.3.4.5.6.7-Heptamethyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,2,3,4,5,6,7-Heptaethyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0036] 1.2.3.4.5.6.7-Heptapropyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,3,4,5,6,7-Heptabutyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0037] 1.2.3.4.5.6.7.8-Octamethyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,2,3,4,5,6,7,8-Octaethyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0038] 1.2.3.4.5.6.7.8-Octapropyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,2,3,4,5,6,7,8-Octabutyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0039] 1.2.2-Trimethyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,2,2-Triethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2-Tripropyl-1 ,2,3,4- Tetrahydroquinoxalin, 1 ,2,2-Tributyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3,3-Trimethyl-1,2,3,4-Tetrahydroquinoxalin,

[0040] 1.3.3-T riethy I- 1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3,3-T ri propyl- 1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3,3-T ributyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,4-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,2,2,4-Tetraethyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0041] 1.2.2.4-Tetrapropyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,4-Tetrabutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,3,4-Penta- methyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,2,2,3,4-Pentaethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,3,4-Pentapropyl-

[0042] 1.2.3.4-Tetrahydroquinoxalin, 1 ,2,2,3,4-Pentabutyl-1,2,3,4-Tetrahydroquinoxalin, 1 , 2, 2,3,3, 4-Hexamethyl-1 , 2,3,4- Tetrahydroquinoxalin, 1 ,2,2,3,3,4-Hexaethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2, 2,3,3, 4-Hexapropyl-1 , 2,3, 4-Tetrahyd- roquinoxalin, 1 ,2,2,3,3,4-Hexabutyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0043] 1.2.2.5-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,5-Tetraethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,5-Tetrapro- pyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,5-Tetrabutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,2,2,6-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 , 2, 2, 6-Tetraethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,6-Tetrapropyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0044] 1.2.2.6-Tetrabutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,7-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,7-Tetra- ethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,7-Tetrapropyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 , 2,2, 7-Tetrabutyl-1 , 2,3,4- Tetrahydroquinoxalin, 1 ,2,2,8-Tetramethyl-l ,2,3,4-Tetrahydroquinoxalin, 1 ,2,2,8-Tetraethyl-1 ,2,3,4-Tetrahydroquino- xalin, 1 ,2,2,8-Tetrapropyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,2,2,8-Tetrabutyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,3,3,5-Tet- ramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,3,3,5-Tetraethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1, 3,3, 5-Tetrapropyl-1, 2,3,4- Tetrahydroquinoxalin, 1 ,3,3,5-Tetrabutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3,3,6-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3,3,6-Tetraethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3,3,6-Tetrapropyl-1 ,2,3,4-Tetrahydroquinoxalin, 1,3,3,6-Tet- rabutyl-1,2,3,4-Tetrahydroquinoxalin, 1,3,3,7-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1, 3,3, 7-Tetraethyl-1 , 2,3,4-

[0045] Tetrahydroquinoxalin, 1 ,3,3,7-Tetrapropyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3,3,7-Tetrabutyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3,3,8-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1 ,3,3,8-Tetraethyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,3,3,8-Tet- rapropyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,3,3,8-Tetrabutyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0046] 1-Ethyl-2,2-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 1-Ethyl-3,3-Dimethyl-1,2,3,4-Tetrahydroquinoxalin, 1,4-Diethyl- 2,2-Dimethyl-1,2,3,4-Tetrahydroquinoxalin, 1 ,4-Diethyl-2,2,3-Trimethyl-1,2,3,4-Tetrahydroquinoxalin, 1,4-Diethyl-

[0047] 2.2.3.3-Tetramethyl-1,2,3,4-Tetrahydroquinoxalin,

[0048] 5-Methoxy-1 ,2,3,4-tetrahydroquinoxalin, 6-Methoxy-1,2,3,4-tetrahydroquinoxalin, 5-Ethoxy-1,2,3,4-tetrahydroquino- xalin, 6-Ethoxy-1 ,2,3,4-tetrahydroquinoxalin, 5-Propoxy-1 ,2,3,4-tetrahydroquinoxalin, 6-Propoxy-1 ,2,3,4-tetrahydroquinoxalin,

[0049] 5-Methoxy-1-methyl-1,2,3,4-tetrahydroquinoxalin, 6-Methoxy-1-methyl-1,2,3,4-tetrahydroquinoxalin, 7-Methoxy-1- methyl-1 ,2,3,4-tetrahydroquinoxalin, 8-Methoxy-1-methyl-1,2,3,4-tetrahydroquinoxalin, 5-Ethoxy-1-methyl-1 , 2,3,4- tetrahydroquinoxalin, 6-Ethoxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Ethoxy-1-methyl-1,2,3,4-tetrahydroquinoxa- lin, 8-Ethoxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 5-Propoxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 6-Propoxy-1- methyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Propoxy-1-methyl-1,2,3,4-tetrahydroquinoxalin, 8-Propoxy-1-methyl-1, 2,3,4- tetrahydroquinoxalin,

[0050] 5-Methoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 6-Methoxy-1-ethyl-1,2,3,4-tetrahydroquinoxalin, 7-Methoxy-1-ethyl-

[0051] 1.2.3.4-tetrahydroquinoxalin, 8-Methoxy-1-ethyl-1,2,3,4-tetrahydroquinoxalin, 5-Ethoxy-1-ethyl-1,2,3,4-tetrahydroqui- noxalin, 6-Ethoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Ethoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 8-Ethoxy-1- ethyl-1 ,2,3,4-tetrahydroquinoxalin, 5-Propoxy-1-ethyl-1,2,3,4-tetrahydroquinoxalin, 6-Propoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Propoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 8-Propoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin,

[0052] 5-Methoxy-2,2-Dimethyl-1,2,3,4-Tetrahydroquinoxalin, 6-Methoxy-2,2-diethyl-1,2,3,4-Tetrahydroquinoxalin, 5-Ethoxy- 2,2-Dimethyl-1,2,3,4-Tetrahydroquinoxalin, 6-Ethoxy-2,2-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 5-Methoxy-1,2,2-tri- methyl-1 ,2,3,4-tetrahydroquinoxalin, 6-Methoxy-1 , 2,2-tri methyl-1 ,2,3,4-tetrahydroquinoxalin, 7-M ethoxy- 1 , 2,2-trime- thyl-1,2,3,4-tetrahydroquinoxalin, 8-Methoxy-1,2,2-trimethyl-1 ,2,3,4-tetrahydroquinoxalin, 5-Ethoxy-1,2,2-trimethyl-

[0053] 1,2,3,4-tetrahydroquinoxalin, 6-Ethoxy-1 ,2,2-trimethyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Ethoxy-1 ,2,2-trimethyl-1,2,3,4- tetrahydroquinoxalin, 8-Ethoxy-1,2,2-trimethyl-1 ,2,3,4-tetrahydroquinoxalin, 5-Methoxy-1,3,3-trimethyl-1,2,3,4- tetrahydroq uinoxal in , 6-Methoxy-1 ,3,3-trimethyl-1 , 2, 3,4-tetrahy d roq uinoxali n, 7-Methoxy-1 , 3,3-tri methyl- 1 ,2,3,4-tetra- hydroquinoxalin, 8- Methoxy- 1 , 3,3-tri methyl- 1 , 2, 3,4-tetrahy d roq uinoxalin , 5-Ethoxy- 1 ,3,3-trimethy 1-1 , 2, 3,4-tetrahydro- quinoxalin, 6-Ethoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxalin, 7-Ethoxy-1 ,3,3-trimethyl-l ,2,3,4-tetrahydroquinoxa- lin, 8-Ethoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxalin,

[0054] 5-Methoxy-1 ,4-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Methoxy-1 ,4-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 5-Ethoxy-

[0055] 1.4-Dimethyl-1,2,3,4-Tetrahydroquinoxalin, 6-Ethoxy-1 ,4-diethyl-1,2,3,4-Tetrahydroquinoxalin,

[0056] 5-Methoxy-1 ,2,2,4-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Methoxy-1 ,2,2,4-Tetramethyl-1 ,2,3,4-Tetrahydroqui- noxalin, 7-Methoxy-1 ,2,2,4-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 8-Methoxy-1 ,2,2,4-Tetramethyl-1 ,2,3,4-Tetra- hydroquinoxalin, 5-Ethoxy-1 ,2,2,4-Tetramethyl-1,2,3,4-Tetrahydroquinoxalin, 6-Ethoxy-1 , 2,2, 4-Tetramethyl-1 , 2,3,4- Tetrahydroquinoxalin, 7-Ethoxy-1 ,2,2,4-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 8-Ethoxy-1 ,2,2,4-Tetramethyl-

[0057] 1.2.3.4-Tetrahydroquinoxalin,

[0058] 5-Hydroxy-1 , 2, 3,4-tetrahydroq ui noxal in , 6-Hydroxy-1 , 2, 3, 4-tetrahy d roqui noxal I n, 5-Ethoxy-1 , 2, 3, 4-tetrahydroqu I noxa- lin, 6-Ethoxy-1,2,3,4-tetrahydroquinoxalin, 5-Propoxy-1 ,2,3,4-tetrahydroquinoxalin, 6-Propoxy-1 ,2,3,4-tetrahydroqui- noxalin,

[0059] 5-Hydroxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 6-Hydroxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Hydroxy-1-me- thyl-1 ,2,3,4-tetrahydroquinoxalin, 8-Hydroxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 5-Ethoxy-1-methyl-1 ,2,3,4-tetra- hydroquinoxalin, 6-Ethoxy-1-methyl-1,2,3,4-tetrahydroquinoxalin, 7-Ethoxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 8- Ethoxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 5-Propoxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 6-Propoxy-1-methyl-

[0060] 1.2.3.4-tetrahydroquinoxalin, 7-Propoxy-1-methyl-1 ,2,3,4-tetrahydroquinoxalin, 8-Propoxy-1-methyl-1 ,2,3,4-tetrahyd- roquinoxalin,

[0061] 5-Hydroxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 6-Hydroxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Hydroxy-1-ethyl-

[0062] 1 ,2,3,4-tetrahydroquinoxalin, 8-Hydroxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 5-Ethoxy-1-ethyl-1 ,2,3,4-tetrahydroqui- noxalin, 6-Ethoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Ethoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 8-Ethoxy-1- ethyl-1 ,2,3,4-tetrahydroquinoxalin, 5-Propoxy-1-ethyl-1,2,3,4-tetrahydroquinoxalin, 6-Propoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Propoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin, 8-Propoxy-1-ethyl-1 ,2,3,4-tetrahydroquinoxalin,

[0063] 5-Hydroxy-2,2-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Hydroxy-2,2-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 5-Ethoxy- 2,2-Dimethyl-1,2,3,4-Tetrahydroquinoxalin, 6-Ethoxy-2,2-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 5-Hydroxy-1 ,2,2-trime- thyl-1 ,2,3,4-tetrahydroquinoxalin, 6-Hydroxy-1 ,2, 2-tri methyl- 1 ,2,3,4-tetrahydroquinoxalin, 7-Hydroxy- 1 ,2, 2-tri methy I-

[0064] 1 ,2,3,4-tetrahydroquinoxalin, 8-Hydroxy-1 ,2, 2-trimethy 1-1 ,2,3,4-tetrahydroquinoxalin, 5-Ethoxy- 1 ,2, 2-trimethy 1-1 ,2,3,4- tetrahydroquinoxalin, 6-Ethoxy- 1 ,2, 2-trimethyl-1 ,2,3,4-tetrahydroquinoxalin, 7-Ethoxy- 1 ,2, 2-trimethy 1-1 ,2,3,4-tetrahydroquinoxalin, 8-Ethoxy- 1 ,2, 2-trimethy I- 1 ,2,3,4-tetrahydroquinoxalin, 5-Hydroxy-1 , 3, 3-trimethy I- 1 ,2,3,4- tetrahydroqu i noxal i n , 6-Hydroxy-1 , 3, 3-trimethy I- 1 ,2, 3, 4-tetrahydroqu i noxal i n, 7-Hy d roxy- 1 , 3,3-trimethyl- 1 , 2, 3,4-tetra- hydroquinoxalin, 8- Hy d roxy-1 , 3,3-tri methy I- 1 , 2, 3, 4-tetrahydroq ui noxal in , 5-Ethoxy- 1 , 3,3-tri methyl- 1 ,2,3,4-tetrahydro- quinoxalin, 6-Ethoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxalin, 7-Ethoxy-1 ,3,3-trimethyl-1 ,2,3,4-tetrahydroquinoxa- lin, 8-Ethoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxalin,

[0065] 5-Hydroxy-1 ,4-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Hydroxy-1 ,4-diethyl-1 ,2,3,4-Tetrahydroquinoxalin, 5-Ethoxy-

[0066] 1.4-Dimethyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Ethoxy-1 ,4-diethyl-1 ,2,3,4-Tetrahydroquinoxalin,

[0067] 5-Hydroxy-1 ,2,2,4-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 6-Hydroxy-1 ,2,2,4-Tetramethyl-1,2,3,4-Tetrahydroqui- noxalin, 7-Hydroxy-1 ,2,2,4-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin, 8-Hydroxy-1 ,2,2,4-Tetramethyl-1 ,2,3,4-Tetrahydroquinoxalin.

[0068] Geeignete Verbindungen der allgemeinen Formel (II) sind beispielsweise 3,4-Dihydroquinoxalin-2(1 H)-on, 1-Methyl-

[0069] 3.4-di hydroqui noxal in-2(1 H)-on, 3-Methyl-3, 4-dihydroquinoxal in-2(1 H)-on, 4-Methy i-3, 4-dihydroquinoxali n-2(1 H)-on,

[0070] 5-Methy l-3,4-dihydroquinoxali n-2(1 H)-on, 6-Methyl-3, 4-di hydroqui noxal in-2(1 H)-on, 7-Methy l-3,4-di hydroquinoxalin- 2(1 H)-on, 8-Methyl-3,4-dihydroquinoxalin-2(1 H)-on, 1-Ethyl-3,4-dihydroquinoxalin-2(1 H)-on, 3-Ethyl-3,4-dihydroqui- noxali n-2(1 H)-on, 4-Ethy I-3, 4-di hy d roqui noxali n-2(1 H)-on, 5-Ethy l-3,4-dihy d roq u i noxal i n-2 (1 H)-on, 6- Ethy l-3,4-di hy d- roqui noxal in-2(1 H)-on, 7-Ethyl-3,4-di hydroqui noxal in-2(1 H)-on, 8-Ethy i-3, 4-di hydroqui noxali n-2(1 H)-on,

[0071] 1-Phenyl-3,4-dihydroquinoxalin-2(1 H)-on, 3-Phenyl-3,4-dihydroquinoxalin-2(1 H)-on, 4-Phenyl-3,4-dihydroquinoxalin- 2(1 H)-on, 5-Pheny i-3, 4-dihydroquinoxali n-2(1 H)-on, 6-Pheny i-3, 4-di hydroquinoxal in-2(1 H)-on, 7-Pheny l-3,4-dihydro- qui noxali n-2(1 H)-on, 8-Pheny l-3,4-di hydroquinoxal in-2(1 H)-on, 1 -Benzy i-3, 4-dihydroquinoxali n-2(1 H)-on, 3-Benzyl-

[0072] 3.4-dihydroqui noxal in-2(1 H)-on, 4-Benzy i-3, 4-dihydroquinoxali n-2(1 H)-on, 5-Benzy l-3,4-di hydroqui noxal in-2(1 H)-on,

[0073] 6-Benzyl-3, 4-dihydroquinoxali n-2(1 H)-on, 7-Benzy i-3, 4-di hydroqui noxal in-2(1 H)-on, 8-Benzy i-3, 4-di hydroquinoxalin- 2(1 H)-on,

[0074] 1.3-D i methy i-3, 4-d i hydroqu i noxal i n-2 (1 H)-on, 1 , 4-D i methy i-3, 4-dihyd roq ui noxali n-2(1 H)-on, 1 , 5-D i methy i-3, 4-di hyd- roquinoxalin-2(1 H)-on, 1,6-Dimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1,7-Dimethyl-3,4-dihydroquinoxalin-2(1 H)-on.

[0075] 1 ,8-Dimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1 ,3-Diethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1,4-Diethyl-3,4-dihydroqui- noxali n-2(1 H)-on, 1 , 5-D iethy i-3, 4-di hyd roqu i noxal i n-2 (1 H)-on, 1 , 6-D iethy i-3, 4-d I hydroqu I noxal I n-2 ( 1 H)-on, 1 ,7-Diet- hy i-3, 4-di hydroqu i noxal i n-2 (1 H)-on. 1 , 8-D i ethy l-3,4-dihyd roq uinoxal in-2(1 H)-on,

[0076] 3.3-Dimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 3,3-Diethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1 ,3,3-Trimethyl-3,4-dihyd- roquinoxalin-2(1 H)-on, 1,3,3-Triethyl-3,4-dihydroquinoxalin-2(1 H)-on, 3,3,4-Trimethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0077] 3.3.4-Triethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1 ,3,3,4-Tetramethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1 ,3,3,4-Tetra- ethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1,3,3,5-Tetramethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1 ,3,3,5-Tetraethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1 ,3,3,6-Tet- ramethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1 ,3,3,6-Tetraethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1,3,3,7-Tetramethyl-3,4- dihydroquinoxalin-2(1 H)-on, 1 ,3,3,7-Tetraethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1,3,3,8-Tetramethyl-3,4-dihydroqui- noxalin-2(1 H)-on, 1 ,3,3,8-Tetraethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1 , 3,3,4, 5-Pentamethyl-3,4-dihydroquinoxalin- 2(1 H)-on, 1 , 3,3, 4, 5-Pentaethy I-3, 4-d i hydroqu i noxal i n-2 (1 H)-on, 1 , 3,3, 4, 6-Pentamethy I -3, 4-di hyd roqu i noxal i n-2(1 H)- on, 1 , 3, 3, 4, 6-Pentaethy l-3,4-d i hydroq ui noxali n-2(1 H)-on, 1 , 3, 3, 4, 7-Pentamethy I-3, 4-d i hydroqu i noxal i n-2(1 H)-on,

[0078] 1.3.3.4.7-Pentaethyl-3,4-dihydroquinoxalin-2(1 H)-on, 1 ,3,3,4,8-Pentamethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0079] 1.3.3.4.8-Pentaethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0080] 5-Methoxy-3, 4-dihydroquinoxali n-2(1 H)-on, 6-Methoxy-3, 4-dihydroquinoxali n-2(1 H)-on, 7-Methoxy-3,4-di hydroquino- xalin-2(1 H)-on, 8-Methoxy-3, 4-dihydroquinoxali n-2(1 H)-on, 5-Ethoxy-3,4-di hydroquinoxal in-2(1 H)-on, 6-Ethoxy-3,4- di hydroquinoxal in-2(1 H)-on, 7-Ethoxy-3, 4-dihydroquinoxal in-2(1 H)-on, 8-Ethoxy-3, 4-di hydroqui noxal in-2(1 H)-on,

[0081] 5-Methoxy-1-methyl-3,4-dihydroquinoxalin-2(1 H)-on, 6-Methoxy-1-methyl-3,4-dihydroquinoxalin-2(1 H)-on, 7-Me- thoxy-1-methyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Methoxy-1-methyl-3,4-dihydroquinoxalin-2(1 H)-on, 5-Ethoxy-1- methyl-3,4-dihydroquinoxalin-2(1 H)-on, 6-Ethoxy-1-methyl-3,4-dihydroquinoxalin-2(1 H)-on, 7-Ethoxy-1-methyl-3,4- dihydroquinoxalin-2(1 H)-on, 8-Ethoxy-1-methyl-3,4-dihydroquinoxalin-2(1 H)-on, 5-Methoxy-3-methyl-3,4-dihydroqui- noxal i n-2 ( 1 H)-on, 6-Methoxy-3-methy i-3, 4-d i hydroq u i noxal i n-2( 1 H)-on, 7- Methoxy-3-methyl-3, 4-d I hydroqu I noxal I n- 2(1 H)-on, 8-Methoxy-3-methy i-3, 4-di hydroquinoxalin-2(1 H)-on, 5-Ethoxy-3-methyl-3, 4-dihydroqui noxal in-2(1 H)-on, 6- Ethoxy-3-methy i-3, 4-dihyd roq ui noxali n-2(1 H)-on, 7-Ethoxy-3-methy i-3, 4-di hyd roqu I noxal I n-2(1 H)-on, 8-Ethoxy-3- methy i-3, 4-di hydroqui noxal in-2(1 H)-on, 5-Methoxy-4-methyl-3,4-di hydroquinoxal in-2(1 H)-on, 6-Methoxy-4-methyl- 3, 4-di hydroqui noxal in-2(1 H)-on,7-Methoxy-4-methy i-3, 4-dihydroquinoxali n-2(1 H)-on, 8-Methoxy-4-methy i-3, 4-dihyd- roquinoxalin-2(1 H)-on, 5-Ethoxy-4-methyl-3,4-di hydroqui noxali n-2(1 H)-on, 6-Ethoxy-4-methy i-3, 4-dihydroqui noxal in- 2(1 H)-on, 7-Ethoxy-4-methy i-3, 4-di hydroqui noxal in-2(1 H)-on, 8-Ethoxy-4-methyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0082] 5-Methoxy-3, 3-dimethy i-3, 4-di hydroqui noxal in-2(1 H)-on, 6-Methoxy-3,3-dimethy i-3, 4-dihydroqui noxali n-2(1 H)-on, 7- Methoxy-3,3-di methy l-3,4-dihydroquinoxalin-2(1 H)-on, 8-Methoxy-3,3-di methy i-3, 4-di hydroquinoxalin-2(1 H)-on, 5- Methoxy-3,3-diethy i-3, 4-dihydroqui noxal in-2(1 H)-on, 6-Methoxy-3, 3-diethy i-3, 4-dihydroqui noxali n-2(1 H)-on, 7-Me- thoxy-3,3-diethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Methoxy-3,3-diethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0083] 5-Methoxy-1 , 3, 3-trimethy i-3, 4-di hydroq uinoxalin-2( 1 H)-on, 6-Methoxy-1 , 3, 3-trimethy i-3, 4-d i hydroqu i noxal i n-2 ( 1 H)-on, 7-Methoxy-1 , 3, 3-trimethy i-3, 4-di hydroq uinoxalin-2( 1 H)-on, 8-Methoxy-1 , 3, 3-trimethy i-3, 4-d i hydroqu i noxal i n-2 ( 1 H)-on, 5-Methoxy-1 , 3, 3-triethy i-3, 4-di hyd roqu i noxal i n-2(1 H)-on, 6-Methoxy-1 , 3, 3-triethy i-3, 4-di hyd roqui noxal i n-2(1 H)-on, 7- Methoxy-1 , 3, 3-triethy I -3, 4-dihy d roq ui noxal i n-2(1 H)-on, 8-Methoxy-1 , 3, 3-triethy I -3, 4-dihyd roq ui noxali n-2(1 H)-on, 5- Methoxy-3,3,4-trimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 6-Methoxy-3,3,4-trimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 7-Methoxy-3,3,4-trimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Methoxy-3,3,4-trimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 5-Methoxy-3, 3, 4-triethy I-3, 4-di hydroquinoxal in-2(1 H)-on, 6-Methoxy-3, 3, 4-triethy I-3, 4-di hydroqui noxal in-2(1 H)-on, 7-

[0084] Methoxy-3,3,4-triethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Methoxy-3,3,4-triethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0085] 5-Methoxy-1 , 3, 3,4-tetramethyl-3, 4-di hyd roqu i noxal i n-2 (1 H)-on, 6-Methoxy-1 , 3, 3, 4-tetramethy I-3, 4-di hyd roqu i noxal i n- 2(1 H)-on, 7-Methoxy-1 , 3, 3,4-tetramethy I-3, 4-d i hydroqu i noxal in-2 ( 1 H)-on, 8-Methoxy-1 , 3, 3, 4-tetramethy I-3, 4-d i hydro- quinoxalin-2(1 H)-on, 5-Methoxy-1 ,3,3,4-tetraethyl-3,4-dihydroquinoxalin-2(1 H)-on, 6-Methoxy-1,3,3,4-tetraethyl-3,4- dihydroquinoxalin-2(1 H)-on, 7-Methoxy-1,3,3,4-tetraethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Methoxy-1 ,3,3,4-tetra- ethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0086] 5-Ethoxy-3,3-dimethy l-3,4-dihydroquinoxali n-2(1 H)-on, 6-Ethoxy-3, 3-di methyl-3, 4-di hydroqui noxal in-2(1 H)-on, 7- Ethoxy-3, 3-di methy i-3, 4-di hydroqui noxal in-2(1 H)-on, 8-Ethoxy-3, 3-dimethy i-3, 4-di hydroqui noxal in-2(1 H)-on, 5- Ethoxy-3, 3-diethy l-3,4-di hydroquinoxal in-2(1 H)-on, 6-Ethoxy-3, 3-diethyl-3, 4-dihydroquinoxali n-2(1 H)-on, 7-Ethoxy-

[0087] 3.3-diethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Ethoxy-3,3-diethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0088] 5-Ethoxy- 1 ,3,3-trimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 6-Ethoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 7- Ethoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Ethoxy-1 ,3,3-trimethyl-3,4-dihydroquinoxalin-2(1 H)-on, 5- Ethoxy-1,3,3-triethyl-3,4-dihydroquinoxalin-2(1 H)-on, 6-Ethoxy-1,3,3-triethyl-3,4-dihydroquinoxalin-2(1 H)-on, 7- Ethoxy-1,3,3-triethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Ethoxy-1,3,3-triethyl-3,4-dihydroquinoxalin-2(1 H)-on, 5- Ethoxy-3, 3,4-tri methy i-3, 4-dihydroquinoxalin-2(1 H)-on, 6-Ethoxy-3,3, 4-trimethy i-3, 4-di hydroquinoxalin-2(1 H)-on, 7- Ethoxy-3, 3,4-tri methy i-3, 4-dihydroquinoxalin-2(1 H)-on, 8-Ethoxy-3,3, 4-trimethy i-3, 4-di hydroquinoxalin-2(1 H)-on, 5- Ethoxy-3, 3, 4-triethy i-3, 4-di hydroqui noxal in-2(1 H)-on, 6-Ethoxy-3, 3, 4-triethy i-3, 4-di hydroquinoxal in-2(1 H)-on, 7- Ethoxy-3,3,4-triethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Ethoxy-3,3,4-triethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0089] 5-Ethoxy- 1 , 3, 3,4-tetramethy i-3, 4-di hydroqu i noxal i n-2(1 H)-on, 6-Ethoxy- 1 , 3, 3,4-tetramethy i-3, 4-di hyd roqu i noxal i n- 2(1 H)-on, 7-Ethoxy-1 , 3, 3,4-tetramethy i-3, 4-d i hydroqu i noxal i n-2 ( 1 H)-on, 8-Ethoxy- 1 , 3, 3, 4-tetramethy i-3, 4-di hyd roqu i- noxali n-2(1 H)-on, 5-Ethoxy- 1 , 3, 3,4-tetraethy i-3, 4-d i hydroqu i noxal in-2(1 H)-on, 6-Ethoxy- 1 , 3, 3, 4-tetraethy i-3, 4-d i hyd- roquinoxalin-2(1 H)-on, 7-Ethoxy-1 ,3,3,4-tetraethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Ethoxy-1,3,3,4-tetraethyl-3,4- di hydroqui noxal in-2(1 H)-on,

[0090] 5-Hydroxy-3, 4-d I hydroqu I noxal I n-2 (1 H)-on, 6-Hyd roxy-3, 4-d I hydroqu I noxal I n-2(1 H)-on, 7- Hy d roxy-3, 4-d i hy d roq uino- xalin-2(1 H)-on, 8-Hydroxy-3,4-dihydroquinoxalin-2(1 H)-on,

[0091] 5-Hydroxy-1 -methyl-3, 4-dihydroquinoxalin-2(1 H)-on, 6-Hydroxy-1 -methyl-3, 4-dihydroquinoxalin-2(1 H)-on, 7-Hydroxy- 1 -methyl-3, 4-dihydroquinoxalin-2(1 H)-on, 8-Hydroxy-1 -methyl-3, 4-dihydroquinoxalin-2(1 H)-on, 5-Hydroxy-3-methyl-

[0092] 3.4-dihydroqui noxal in-2(1 H)-on, 6-Hydroxy-3-methy i-3, 4-di hydroqui noxal in-2(1 H)-on, 7-Hydroxy-3-methyl-3,4-di hydroquinoxal in-2(1 H)-on, 8-Hydroxy-3-methy i-3, 4-di hydroquinoxalin-2(1 H)-on, 5-Hydroxy-4-methyl-3,4- di hydroquinoxalin-2(1 H)-on, 6-Hydroxy-4-methyl-3, 4-dihydroquinoxali n-2(1 H)-on, 7-Hydroxy-4-methyl-3,4-dihydroqui- noxal i n-2 ( 1 H)-on, 8-Hydroxy-4-methy I-3, 4-d i hydroq uinoxal in-2 ( 1 H)-on,

[0093] 5- Hy d roxy-3,3-dimethy I-3, 4-d i hydroqu i noxal i n-2 ( 1 H)-on, 6-Hyd roxy-3, 3-di methy I-3, 4-dihy droq u i noxal i n-2 (1 H)-on, 7- Hyd roxy-3, 3-d i methy I-3, 4-di hydroqui noxal in-2(1 H)-on, 8-Hydroxy-3, 3-dimethyl-3, 4-dihydroquinoxali n-2(1 H)-on, 5- Hydroxy-3, 3-diethyl-3, 4-dihydroquinoxali n-2(1 H)-on, 6-Hy droxy-3,3-diethy i-3, 4-di hydroquinoxal in-2(1 H)-on, 7-Hyd- roxy-3,3-diethyl-3,4-dihydroquinoxalin-2(1 H)-on, 8-Hydroxy-3,3-diethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0094] 5-Hydroxy-1 , 3, 3-trimethy i-3, 4-d i hydroqu i noxal in-2 ( 1 H)-on, 6-Hydroxy-1 , 3,3-trimethyl-3, 4-d i hydroqu i noxal i n-2 (1 H)-on, 7-Hydroxy-1 , 3, 3-trimethyl-3, 4-d i hydroqu i noxal in-2 ( 1 H)-on, 8-Hydroxy-1 , 3,3-trimethyl-3, 4-d i hydroqu i noxal i n-2 (1 H)-on, 5-Hydroxy-1 , 3, 3-triethy I -3, 4-dihy d roq ui noxali n-2(1 H)-on, 6-Hydroxy-1 , 3, 3-triethyl-3, 4-di hyd roq ui noxal i n-2(1 H)-on, 7- Hydroxy-1 , 3,3-triethy l-3,4-dihy d roq uinoxalin-2(1 H)-on, 8-Hydroxy-1 , 3,3-triethyl-3,4-di hydroq uinoxalin-2 ( 1 H)-on, 5- Hyd roxy-3, 3, 4- tri methy l-3,4-dihydroquinoxalin-2(1 H)-on, 6- Hyd roxy-3, 3, 4-trimethyl-3, 4-dihydroquinoxali n-2(1 H)-on, 7- Hyd roxy-3, 3, 4- tri methy l-3,4-dihydroquinoxalin-2(1 H)-on, 8- Hyd roxy-3, 3, 4-trimethyl-3, 4-dihydroquinoxali n-2(1 H)-on, 5- Hydroxy-3,3,4-triethy I-3, 4-di hydroquinoxal in-2(1 H)-on, 6- Hydroxy-3, 3, 4-triethy l-3,4-di hydroquinoxalin-2(1 H)-on, 7- Hydroxy-3,3,4-triethyl-3,4-dihydroquinoxalin-2(1 H)-on,8-Hydroxy-3,3,4-triethyl-3,4-dihydroquinoxalin-2(1 H)-on,

[0095] 5-Hydroxy-1 , 3, 3,4-tetramethyl-3, 4-di hyd roqu i noxal i n-2(1 H)-on, 6-Hydroxy-1 , 3,3, 4-tetramethy I -3, 4-dihy d roqui noxal i n- 2(1 H)-on, 7-Hydroxy-1 , 3, 3,4-tetramethyl-3, 4-d i hydroqu i noxal i n-2 (1 H)-on, 8-Hydroxy-1 , 3, 3, 4-tetramethy I-3, 4-di hydroqui noxali n-2(1 H)-on, 5-Hydroxy-1 , 3, 3,4-tetraethy I-3, 4-d i hydroqu i noxal i n-2 ( 1 H)-on, 6-Hydroxy-1 ,3,3, 4-tetraethyl-3, 4- di hydroq u i noxal i n-2( 1 H)-on, 7-Hydroxy-1 , 3, 3, 4-tetraethy l-3,4-dihy d roq uinoxali n-2(1 H)-on, 8-Hydroxy-1 ,3, 3, 4-tetra- ethyl-3,4-dihydroquinoxalin-2(1 H)-on.

[0096] Die Verbindung der allgemeinen Formel (I) ist bevorzugt 7-Methoxy-1 ,3,3-trimethyl-1 ,2,3,4-tetrahydroquinoxalin, 6- Methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxalin, 6-Methoxy-1, 2, 2, 4-tetramethyl-1 ,2,3,4-tetrahydroquinoxalin oder 7-Methoxy-1 ,2,2,4-tetramethyl-1 ,2,3,4-tetrahydroquinoxalin. Die Verbindung der allgemeinen Formel (II) ist bevorzugt 3, 3-D i methy I-3, 4-di hyd roqui noxal i n-2(1 H)-on, 7-Methoxy-3, 3-d i methy I-3, 4-dihy d roq ui noxali n-2(1 H)-on, 6- Methoxy-3, 3-di methy I-3, 4-d i hyd roq uinoxali n-2(1 H)-on, 7-Methoxy-1 , 3, 3-trimethy I-3, 4-d i hydroqu i noxal i n-2 (1 H)-on oder 6-Methoxy-1 , 3, 3-trimethyl-3, 4-d i hydroqu i noxal i n-2 ( 1 H)-on.

[0097] In the mixture, the total amount of the compounds of the general formula (I) or (II) is preferably from 0.0001 to 0.1000 wt.%, preferably from 0.0002 to 0.0750 wt.%, particularly preferably from 0.0005 to 0.0500 wt.%, very particularly preferably from 0.0010 to 0.0250 wt.%, in each case based on the total amount of polymerizable carbonyl compounds.

[0098] It is conceivable that a mixture of compounds of general formula (I) and / or (II) is used in the mixture according to the invention. The statement of the total amount of compounds of general formula (I) or (II) then refers to the total amount of the mixture of compounds of general formula (I) and / or (II). For example, a mixture of 7-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one and 6-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one (in each case general formula II) or a mixture of 7-methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxaline and 6-methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxaline (in each case general formula I) can be used.

[0099] In the mixture, the total amount of polymerizable carbonyl compounds is preferably at least 50% by weight, preferably at least 80% by weight, particularly preferably at least 98% by weight, very particularly preferably at least 99% by weight, in each case based on the total weight of the mixture.

[0100] Polymerizable carbonyl compounds are preferably mono-, di- or triethylenically unsaturated C3 to Cs carboxylic acids, mono-, di- or triethylenically unsaturated C3 to Cs aldehydes, mono-, di- or triethylenically unsaturated C3 to Cs carboxylic acid esters having 1 to 20 carbon atoms in the ester groups, mono-, di- or triethylenically unsaturated C3 to Cs carboxylic acid amides, mono-, di- or triethylenically unsaturated C3 to Cs nitriles, mono-, di- or triethylenically unsaturated C3 to Cs carboxylic acid anhydrides, vinyl esters of saturated C2 to C2o carboxylic acids, vinyl ethers of saturated C1 to C20 alcohols, vinyl aromatics, vinyl heteroaromatics, vinyl lactams having 3 to 10 Carbon atoms in the ring, open-chain N-vinylamide compounds and N-vinylamine compounds, vinyl halides, aliphatic, optionally halogenated hydrocarbons with 2 to 8 carbon atoms and 1 or 2 ethylenic double bonds,Vinylidenes or any mixtures of two or more of the aforementioned compounds.

[0101] Particularly preferred are mono-, di- or triethylenically unsaturated C3- to C5-carboxylic acids, for example acrylic acid, methacrylic acid, dimethacrylic acid, ethacrylic acid, citraconic acid, methylenemalonic acid, crotonic acid, fumaric acid, mesaconic acid, itaconic acid and maleic acid, mono-, di- or triethylenically unsaturated C3- to C5-carboxylic acid esters having 1 to 20 carbon atoms in the ester groups, for example acrylic acid esters with C1- to C20-alkyl, methacrylic acid esters with C1- to C20-alkyl, dimethacrylic acid esters with C1- to C20-alkyl, ethacrylic acid esters with C1- to C20-alkyl, citraconic acid esters with C1- to C20-alkyl, methylenemalonic acid esters with C1- to C20-alkyl, crotonic acid esters with C1- to C20-alkyl, fumaric acid esters with C1- to C20-alkyl, mesaconic acid esters with Ci- to C2o-alkyl, itaconic acid esters with Ci- to C20-alkyl and maleic acid esters with Ci- to C2o-alkyl, mono-, di- or triethylenically unsaturated C3- to Cs-carboxylic acid amides, for example acrylamide, methacrylamide,Dimethacrylamide, ethacrylamide, citraconicamide, methylenemalonicamide, crotonicamide, fumaramide, mesaconicamide, itaconicamide, and maleamide, mono-, di-, or triethylenically unsaturated C3- to C8-nitriles, for example acrylonitrile and methacrylonitrile, and mono-, di-, or triethylenically unsaturated C3- to C8-carboxylic anhydrides, for example acrylic anhydride, methacrylic anhydride, itaconic anhydride, and maleic anhydride. Very particular preference is given to acrylic acid, methacrylic acid, acrylic acid esters with C1- to C8-alkyl, such as methyl acrylate, ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate, and methacrylic acid esters with C1- to C8-alkyl, such as methyl methacrylate.

[0102] Other suitable polymerizable carbonyl compounds are dipropylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, glycerol triacrylate, ethoxylated glycerol triacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, butanediol monoacrylate, dicyclopentadienyl acrylate, 2-dimethylaminoethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate.

[0103] With acrylic acid as the polymerizable carbonyl compound, the total amount of the compounds of the general formula (I) or (II) in the mixture is preferably from 0.0050 to 0.1000 wt.%, preferably from 0.0100 to 0.0750 wt.%, particularly preferably from 0.0120 to 0.0500 wt.%, very particularly preferably from 0.0150 to 0.0250 wt.%, in each case based on acrylic acid.

[0104] With methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate and / or 2-ethylhexyl acrylate as polymerizable carbonyl compound, the total amount of the compounds of the general formula (I) or (II) in the mixture is preferably from 0.0001 to 0.0100 wt.%, preferably from 0.0002 to 0.0075 wt.%, particularly preferably from 0.0005 to 0.0050 wt.%, very particularly preferably from 0.0010 to 0.0020 wt.%, in each case based on the total amount of methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate and / or 2-ethylhexyl acrylate.

[0105] The mixture according to the invention preferably contains less than 0.0001 wt.% of a manganese salt, a copper salt, a 2,2,6,6-tetramethylpiperidine compound, an N-oxyl compound and a nitroso compound, each based on the total amount of the mixture.

[0106] A further object of the present invention is the use of at least one compound of the general formula (I) or (II), as defined above, for inhibiting the polymerization of at least one polymerizable carbonyl compound.

[0107] In a preferred embodiment of the present invention, the compound of general formula (I) or (II) is used essentially as the sole polymerization inhibitor.

[0108] A further object of the present invention is a process for the storage and / or transport of a mixture comprising at least one compound of the general formula (I) or (II), as defined above, and at least one polymerizable carbonyl compound.

[0109] The mixture is typically stored and / or transported in an oxygen-containing atmosphere. The mixture is preferably stored in a container under an oxygen-containing atmosphere with an oxygen content of 5 to 10 vol.%, and the mixture is regularly circulated within the container, for example, by completely pumping the tank contents around at least once a week. The relatively low oxygen content prevents flammable gas mixtures in the container. Circulation replaces consumed dissolved oxygen in the liquid polymerizable compound.

[0110] Mixtures according to the invention with acrylic acid as the polymerizable carbonyl compound are particularly suitable for the production of water-swellable polyacrylic acids (superabsorbents) and water-soluble polyacrylic acids. The production of superabsorbents is described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 6th edition, Volume 35, pages 73 to 93.

[0111] Mixtures according to the invention with methyl acrylate, ethyl acrylate, n-butyl acrylate or 2-ethylhexyl acrylate as polymerizable carbonyl compound are particularly suitable for the preparation of polymer dispersions.

[0112] The present invention further relates to a process for radical polymerization, wherein one of the mixtures described above is polymerized by means of a polymerization initiator, and to the use of one of the mixtures described above for radical polymerization by means of a polymerization initiator.

[0113] By means of the radical polymerization according to the invention, for example, water-soluble and water-swellable polyacrylic acids and their sodium salts are obtainable.

[0114] Radical polymerization itself is well known and is usually carried out in solution. Suitable polymerization initiators include all compounds that can decompose into radicals under the chosen reaction conditions, for example, thermal initiators, redox initiators, and photoinitiators. Suitable thermal initiators are peroxomono- and disulfates, as well as peroxomono- and diphosphates. Suitable redox initiators are sodium peroxodisulfate / ascorbic acid, hydrogen peroxide / ascorbic acid, sodium peroxodisulfate / sodium hypophosphite, sodium peroxodisulfate / sodium bisulfite, and hydrogen peroxide / sodium bisulfite.

[0115] Another object of the invention is a compound of the general formula (I) where

[0116] R1 , R 2 , R 3 and R 4 independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C20-alkoxy, aryl, aryloxy, benzyl, hydroxy, nitro, cyano, amino or halide, wherein at least one of R 1 , R 2 , R 3 or R 4 there is no H,

[0117] R 5 Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl,

[0118] R 6 and R 7 independently of each other is Ci- to C2o-alkyl and R 8 and R 9 independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide or R 6 and R 7 independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide and R 8 and R 9independently of each other is Ci- to C2o-alkyl and R 10 Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl, preferably for polymerization inhibition.

[0119] Preferred is R 1 , R 2 , R 3 and R 4 independently of one another H, Ci- to C lkyl or Ci- to C alkoxy, R 5 Ci- to C3-alkyl, R 6 and R 7 independently of each other Ci- to C lkyl and R 8 and R 9 independently of one another H or Ci- to C4-alkyl or R 6 and R 7 independently of each other H or Ci- to C lkyl and R 8 and R 9 independently of one another Ci- to C4-alkyl and R 10 Ci- to C3-alkyl.

[0120] Further preferred is R 1 and R 4 H, R 2 and R 3 independently of one another Ci- to C4-alkoxy, R 5 Ci- to C2-alkyl, R 6 and R 7 independently of one another Ci- to Ca-alkyl and R 8 and R 9independently H or R 6 and R 7 independently of each other H and R 8 and R 9 independently of one another Ci- to Ca-alkyl and R 10 Ci- to C2-alkyl.

[0121] Preferably, R 1 , R 2 and R 4 H and R 3 Methoxy or R 1 , R 3 and R 4 H and R 2 Methoxy, R 5 Methyl, R 6 and R 7 H, R 8 and R 9 Methyl and R 10 Methyl.

[0122] Particularly preferred is R 1 , R 2 and R 4 H, R 3 Methoxy, R 5 Methyl, R 6 and R 7 H, R 8 and R 9 Methyl and R 10 Methyl (6-methoxy-1,2, 2,4-tetramethy I-1, 2, 3,4-tetrahydroq uinoxal in).

[0123] This disclosure regarding the compound of general formula (I) alone is not to be understood as a limitation of the disclosure regarding the compound of general formula (I) in the mixture according to the invention.

[0124] Examples

[0125] Preparation of 7-methoxy-3,3-dimethyl-3,4-dihydroquinoxalin-2(1H)-one and 6-methoxy-3,3-dimethyl-3,4-dihydroquinoxalin-2(1H)-one A solution of 4-methoxy-o-phenylenediamine (3.00 g, 21.7 mmol, 1.0 equiv), 1,1,1-trichloro-2-methyl-2-propanol (9.63 g, 54.3 mmol, 2.5 equiv), and benzyltriethylammonium chloride (0.50 g, 2.2 mmol, 0.1 equiv) was dissolved in 145 mL of dichloromethane and cooled to 0°C under nitrogen. Subsequently, a sodium hydroxide solution (50%, 2.86 mL) was added within two minutes. The reaction mixture was warmed to room temperature overnight. After two days at room temperature, 50 mL of water was added, the phases were separated, and the aqueous phase was extracted again with dichloromethane (2 x 50 mL). The combined organic phases were dried (MgSiCl), and the solvent was removed under reduced pressure. The crude product was purified by column chromatography (silica gel, cyclohexane / ethyl acetate, gradient).A mixture of the two isomers 7-methoxy-3,3-dimethyl-3,4-dihydroquinoxalin-2(1 H)-one and 6-methoxy-3,3-dimethyl-3,4-dihydro- quinoxalin-2(1 H)-one (ratio 70:30, 3.46 g, 16.8 mmol, 77%) was obtained as a yellow-orange solid.

[0126] Preparation of 7-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one and 6-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one

[0127] The mixture of the two isomers 7-methoxy-3,3-dimethyl-3,4-dihydroquinoxalin-2(1H)-one and 6-methoxy-3,3-dimethyl-3,4-dihydroquinoxalin-2(1H)-one (ratio 70:30, 1.00 g, 4.85 mmol, 1.0 equiv) was dissolved in DMF (19 mL). Cesium carbonate (2.37 g, 7.3 mmol, 1.5 equiv) and methyl iodide (1.38 g, 9.7 mmol, 2.0 equiv) were then added and stirred at room temperature for 3 hours. After addition of 25 mL of ethyl acetate and 25 mL of water, the phases were separated, and the organic phase was washed with saturated sodium chloride solution. The organic phase was dried (MgSO4), and the solvent was removed under reduced pressure. The crude product obtained was purified by column chromatography (silica gel, cyclohexane / ethyl acetate, gradient). A mixture of the two isomers 7-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one and 6-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one (ratio 70:30, 0.88 g, 3.97 mmol, 82%) was obtained as an orange oil.

[0128] Preparation of 7-methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxaline and 6-methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxaline

[0129] Under nitrogen, a mixture of the two isomers 7-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one and 6-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one (ratio 70:30, 0.59 g, 2.7 mmol, 1.0 equiv) was dissolved in dichloromethane (27 mL). A solution of diisobutylaluminum hydride in toluene (1 mol / L, 10.7 mL, 10.7 mmol, 4.0 equiv) was then added dropwise, and the reaction mixture was stirred at room temperature. After 5 hours, the mixture was cooled to 0°C, and dichloromethane (20 mL) and sodium hydroxide solution (2 mol / L, 20 mL) were added. The phases were separated, and the aqueous phase was extracted with dichloromethane (2 x 20 mL). The combined organic phases were dried (Na2SO4), and the solvent was removed under reduced pressure. The crude product was purified by column chromatography (silica gel, cyclohexane / ethyl acetate, gradient). The two isomers could be isolated separately.The isomer 7-methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxaline (0.29 g, 1.41 mmol, 52%) was obtained as a grey solid, the isomer 6-methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxaline (0.13 g, 0.63 mmol, 23%) was obtained as an orange oil.

[0130] Preparation of 6-methoxy-1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinoxaline

[0131] A mixture of the two isomers 7-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one and 6-methoxy-1,3,3-trimethyl-3,4-dihydroquinoxalin-2(1H)-one (ratio 70:30, 4.84 g, 22.0 mmol, 1.0 equiv) was dissolved in DMF (90 mL). Cesium carbonate (2.37 g, 7.3 mmol, 1.5 equiv) and methyl iodide (1.38 g, 9.7 mmol, 2.0 equiv) were then added, and the mixture was stirred at room temperature for 3 hours. After addition of 25 mL of ethyl acetate and 25 mL of water, the phases were separated, and the organic phase was washed with saturated sodium chloride solution. The organic phase was dried (MgSO4), and the solvent was removed under reduced pressure. The crude product obtained was used in the next step without further purification.

[0132] The crude product from the previous reaction was dissolved in dichloromethane (220 mL). A solution of diisobutylaluminum hydride in toluene (1 mol / L, 88 mL, 88 mmol, 4.0 equiv) was then added dropwise, and the reaction mixture was stirred at room temperature. After 5 hours, the mixture was cooled to 0°C, and dichloromethane (200 mL) and sodium hydroxide solution (2 mol / L, 200 mL) were added. The phases were separated, and the aqueous phase was extracted with dichloromethane (2 x 200 mL). The combined organic phases were dried (Na2SO4), and the solvent was removed under reduced pressure. The crude product obtained was purified by column chromatography (silica gel, cyclohexane / ethyl acetate, gradient). The two isomers could be isolated separately. The product 6-methoxy-1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinoxaline (1.34 g, 6.1 mmol, 28%) was obtained as an orange oil. Furthermore, the isomer 7-methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxaline (0.1 g) was obtained.52 g, 2.52 mmol, 11%) and the isomer 6-methoxy-1, 3, 3-trimethyl-1, 2,3, 4-tetrahydroquinoxaline (0.78 g, 3.8 mmol, 17%) were isolated.

[0133] Experiments on polymerization inhibition

[0134] The monomer used was distilled twice to remove the polymerization inhibitor MEHQ. The resulting monomer was then treated with the specified amount of the polymerization inhibitor.

[0135] 0.5 ml of each mixture was filled into a 1.8 ml ampoule and stored at the specified temperature in a convection oven. In each test series, three ampoule of each mixture were filled and tested, with the time required for complete polymerization being recorded visually. The average of the three recorded times is given.

[0136] The results are summarized in Tables 1 to 4:

[0137] Table 1 : Mixtures with acrylic acid

[0138] MEHQ: Hydroquinone monomethyl ether *) Comparative example

[0139] Table 2: Mixtures with methacrylic acid

[0140] MEHQ: Hydroquinone monomethyl ether *) Comparative example

[0141] Table 3: Mixtures with ethyl acrylate MEHQ: hydroquinone monomethyl ether

[0142] *) Comparative example Table 4: Mixtures with n-butyl acrylate

[0143] MEHQ: hydroquinone monomethyl ether

[0144] *) Comparison example

[0145] The polymerization inhibitors according to the invention have improved or at least comparable efficacy compared to MEHQ.

[0146] Polymerization experiments

[0147] Under a nitrogen atmosphere, 450 g of water were placed in a reaction vessel. The reaction mixture was heated to 95°C with stirring. Once the temperature reached 95°C, three streams were added while stirring and maintaining the temperature.

[0148] Stream 1 : Dosage over 5 h, 500 g acrylic acid

[0149] Stream 2: Dosage over 4.75 h, 15 g sodium hypophosphite in 35 g deionized water

[0150] Stream 3: Dosage over 5.25 h, 5 g sodium peroxodisulfate in 66.4 g deionized water. After addition of the three streams, the reaction mixture was stirred for another hour at 95°C. The reaction mixture was then cooled to room temperature and 80 g of water were added.

[0151] The acrylic acid used in stream 1 was stabilized with 200 wt. ppm of 3,3-dimethyl-3,4-dihydroquinoxalin-2(1 H)-one or 0.02 wt.% MEHQ.

[0152] The obtained polymers were analyzed by GPC (calibration with Na-PAA standard, eluent 0.01 mol / l phosphate buffer, pH=7.4 in distilled water, with 0.01 M NaNa).

[0153] The results are summarized in Table 5:

[0154] Table 5: Polymerization of acrylic acid

[0155] MEHQ: hydroquinone monomethyl ether

[0156] *) Comparison example

[0157] The polymerization inhibitor according to the invention resulted in a polyacrylic acid with comparable molecular weight.

Claims

Patent claims 1. Mixture containing at least one compound of general formula (I) where R 1 , R 2 , R 3 and R 4 independently of one another H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy, nitro, cyano, amino or halide, R 5 H, Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl, R 6 , R 7 , R 8 and R 9 independently of one another H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide and R 10 H, Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl, or a compound of the general formula (II) R 11 , R 12 , R 13 and R 14independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy, nitro, cyano, amino or halide, R 15 H, Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl, R 16 and R 17 independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C20-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide and R 18 H, Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl, and at least one polymerizable carbonyl compound, wherein the total amount of polymerizable carbonyl compounds in the mixture is at least 30 wt.%, based on the total weight of the mixture.

2. Mixture according to claim 1, characterized in that R 1 , R 2 , R 3 and R 4independently of one another is H, Ci- to Cio-alkyl, Ci- to Cw-alkoxy, hydroxy or halide, R 5 H or Ci- to Cw-alkyl, R 6 , R 7 , R 8 and R 9 independently of one another is H, Ci- to Cw-alkyl, Ci- to Cw-alkoxy, hydroxy or halide and R 10 H or Ci- to Cw-alkyl, and R 11 , R 12 , R 13 and R 14 independently of one another is H, Ci- to Cw-alkyl, Ci- to Cw-alkoxy, hydroxy or halide, R 15 H or Ci- to Cw-alkyl, R 16 and R 17 independently of one another is H, Ci- to Cw-alkyl, Ci- to Cw-alkoxy, hydroxy or halide and R 18 H or Ci- to Cw-alkyl.

3. Mixture according to claim 1, characterized in that R 1 , R 2 , R 3 and R 4 independently of one another is H, Ci- to Ce-alkyl or Ci- to Ce-alkoxy, R 5 H or Ci- to Ce-alkyl, R 6 , R 7 , R 8and R 9 independently of one another is H, Ci- to Ce-alkyl or Ci- to Ce-alkoxy and R 10 H or Ci- to Ce-alkyl, and R 11 , R 12 , R 13 and R 14 independently of one another is H, Ci- to Ce-alkyl or Ci- to Ce-alkoxy, R 15 H or Ci- to Ce-alkyl, R 16 and R 17 independently of one another is H, Ci- to Ce-alkyl or Ci- to Ce-alkoxy and R 18 H or Ci- to Ce-alkyl.

4. Mixture according to claim 1, characterized in that R 1 , R 2 , R 3 and R 4 independently of one another is H, Ci- to C alkyl or Ci- to C ikoxy, R 5 H or Ci- to Ce-alkyl, R 6 , R 7 , R 8 and R 9 independently of one another is H, Ci- to C lkyl or Ci- to C4-alkoxy and R 10 H or Ci- to Ce-alkyl, and R 11 , R 12 , R 13 and R 14independently of one another is H, Ci- to C4-alkyl or Ci- to C4-alkoxy, R 15 H or Ci- to Ce-alkyl, R 16 and R 17 independently of one another is H, Ci- to C4-alkyl or Ci- to C4-alkoxy and R 18 H or Ci- to Ce-alkyl.

5. Mixture according to claim 1, characterized in that the compound of the general formula (I) is 7-methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxaline, 6-methoxy-1,3,3-trimethyl-1,2,3,4-tetrahydroquinoxaline, 6-methoxy-1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinoxaline or 7-methoxy-1,2,2,4-tetramethyl-1,2,3,4-tetrahydroquinoxaline and the compound of the general formula (II) is 3,3-dimethyl-3,4-dihydroquinoxalin-2(1H)-one, 7-methoxy-3,3-dimethyl-3,4-dihydroquinoxalin-2(1 H)-one, 6-methoxy-3,3-di methy I-3, 4-di hydroquinoxal in-2(1 H)-one, 7-methoxy-1, 3, 3-trimethyl-3, 4-d I hydroqui noxal i n-2 (1 H)-one or 6-methoxy-1, 3, 3-trimethoxy i-3, 4-di hydroq uinoxalin-2(1H)-one is.

6. Mixture according to one of claims 1 to 5, characterized in that the total amount of the compounds of the general formula (I) or (II) in the mixture is from 0.0001 to 0.1000 wt.%, based on the total amount of polymerizable carbonyl compounds.

7. Mixture according to one of claims 1 to 6, characterized in that the total amount of polymerizable carbonyl compounds in the mixture is at least 98 wt.%, based on the total weight of the mixture.

8. Mixture according to one of claims 1 to 7, characterized in that the polymerizable carbonyl compound is acrylic acid and / or methacrylic acid.

9. Mixture according to claim 8, characterized in that the total amount of the compounds of general formula (I) or (II) in the mixture is from 0.0050 to 0.1000 wt.%, based on the total amount of acrylic acid and / or methacrylic acid.

10. Mixture according to one of claims 1 to 7, characterized in that the polymerizable carbonyl compound is methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate and / or 2-ethylhexyl acrylate.

11. Mixture according to claim 10, characterized in that the total amount of the compounds of the general formula (I) or (II) in the mixture is from 0.0001 to 0.0100 wt.%, based on the total amount of methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate and / or 2-ethylhexyl acrylate.

12. Use of at least one compound of general formula (I) or (II) according to any one of claims 1 to 5 for inhibiting the polymerization of at least one polymerizable carbonyl compound.

13. A method for storing and / or transporting a mixture according to any one of claims 1 to 11.

14. Compound of general formula (I) where R 1 , R 2 , R3 and R 4 independently of one another is H, Ci- to C2o-alkyl, Ci- to C2o-acyl, Ci- to C2o-acyloxy, Ci- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy, nitro, cyano, amino or halide, wherein at least one of R 1 , R 2 , R 3 or R 4 there is no H, R 5 Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl, R 6 and R 7 independently of each other is Ci- to C2o-alkyl and R 8 and R 9 independently of one another is H, C1- to C20-alkyl, C1- to C20-acyl, C1- to C20-acyloxy, C1- to C20-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide or R 6 and R 7 independently of one another is H, C1- to C2o-alkyl, C1- to C2o-acyl, C1- to C2o-acyloxy, C1- to C2o-alkoxy, aryl, aryloxy, benzyl, hydroxy or halide and R 8 and R 9 independently of each other is Ci- to C20-alkyl and R 10Ci- to C2o-alkyl, Ci- to C2o-acyl or aryl.

15. A compound according to claim 14, characterized in that R 1 , R 2 and R 4 H is, R 3 Methoxy is, R 5 Methyl is, R 6 and R 7 H is, R 8 and R 9 Methyl and R 10 is methyl.

Images